1. Field of the Invention
The present invention is in the field of lasers. In particular the invention is in the field of fibers that function in the mid-IR range.
2. Description of the Related Technology
In the mid-IR range of the optical spectrum, in particular within the 3.0 μm to 5.0 μm wavelength region of the optical spectrum, there are possible applications in remote sensing and environmental monitoring, for example.
In the past, rare earth doped chalcogenide fibers have been shown to be strong emitters of mid-IR radiation. The phonon energy of chalcogenide glasses is within the range of 200-350 cm−1, which is low when compared to fluoride fiber, which has a phonon energy of ˜560 cm−1 and silica fiber, which has a phonon energy of ˜1100 cm−1. The low phonon energy allows many transitions to occur which are typically quenched in fluoride and silica fiber. To date, however, laser action in these materials has only been demonstrated in the near-IR at wavelengths of 1 μm. Much spectroscopy has been done to assess whether the fibers are viable for development of lasers and amplifiers in the mid-IR wavelengths. While the spectroscopy indicates that the materials show promise, a product that uses practical pumping schemes, has good cavity characteristics and laser dynamics has not yet been effectively created.
Therefore there is a need for a laser apparatus that uses a fiber and is able to effectively use the 4.5 μm to 5.0 μm wavelength region of the optical spectrum in order to create is an efficient, compact and rugged light source for this spectral region.